1. Field of the Invention
The present invention relates to a semiconductor light-emitting device including a current confinement layer formed by oxidation and a method of manufacturing the same, and particularly to a semiconductor light-emitting device suitable for a red laser having a wavelength of about 600 nm to 700 nm and a method of manufacturing thereof.
2. Description of the Related Art
A laser diode using AlGaInP as a base material can obtain red emission having a wavelength of 600 nm to 700 nm and is widely used as a light source for a high-density recording by DVD (Digital Versatile Disc) or the like.
The red laser using AlGaInP is generally formed with a strip-shaped ridge by removing part of a p-type semiconductor layer by etching for current confinement. Upon directly forming an electrode on the ridge, leakage current is generated. Therefore, in order to prevent the leakage current, a buried layer including an n-type GaAs layer or a laminated structure of an n-type AlInP layer and an n-type GaAs layer, or an insulating layer made of silicon dioxide (SiO2), silicon nitride (SiN) or the like is formed on a side surface of the ridge.
However, the current confinement by the ridge of the related art has a several problems as mentioned below. For example, n-type GaAs used for a material of the buried layer has a bandgap width of 1.42 eV (873 nm). Therefore, n-type GaAs absorbs the light of a wavelength of 600 nm to 700 nm and absorption loss of the light generated in an active layer becomes large. In addition, a dielectric material such as silicon dioxide has a large difference in a lattice constant with the semiconductor, so the insulating layer formed near the active layer largely distorts the active layer. The absorption loss of the light or the distortion of the active layer increases the amount of oscillation current and largely decreases reliability of the device.
In order to reduce the amount of the oscillation current, a current injection region in the active layer is narrowed by reducing the width of the base of the ridge to reduce the volume of the emission part. However, generally, the ridge is formed by chemical etching, so it is necessary to make the width of the top of the ridge smaller than the width of the base of the ridge. For example, when the width of the base of the ridge is about 2 μm to 3 μm, the width of the top of the ridge is 1.0 μm or less. This results in an increase in operation voltage, thereby power consumption is increased. The increased power consumption largely affects on the device life and this will be a serious problem for a practical application.
To solve these problems, a method that part of a Group III-V compound semiconductor layer containing aluminum (Al) is oxidized by water vapor at a temperature of 375° C. or higher to form the current confinement layer has been proposed (referred to U.S. Pat. Nos. 5,262,360 and 5,373,522; Japanese Patent No. 3,097,863; and J. M. Dallesasse et al., “Native-oxide stripe-geometry AlxGa1-xAs-GaAs quantum well heterostructure lasers”, Applied Physics Letters, American Institute of Physics, Jan. 28, 1991, vol. 58, No. 4, pp. 394-396).
However, the volume of the current confinement layer formed by oxidation shrinks and generates distortion in the semiconductor layers including the active layer formed above and below the current confinement layer. The distortion adversely affects on the device characteristics and reliability, in particular, the device life is significantly deteriorates. Therefore, when using the current confinement layer formed by oxidation, there is still room for an improvement in conditions such as the device structure and the oxidation temperature.